Space debris networks

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Description/Abstract

There are 3,226 satellites and over 10,000 items of man-made space debris, larger than 10 cm, in orbit around the Earth. Whilst most debris has been generated by explosions, modelling studies suggest that collisions will soon take over as the main debris generating source. Irrespective of its source, debris poses a collision risk to operational satellites and other debris objects. Even a single collision (involving satellites and/or debris) has the potential to create many hundreds of new debris objects which would have long-term negative implications for satellite operators and services.Space debris mitigation guidelines are currently in place to limit the production of new debris. In addition to these guidelines, Active Debris Removal (ADR) may be needed to reduce the number of debris objects in orbit. However, if debris objects are to be removed by ADR then a robust and quantitative method will be required to identify objects most likely to have a negative impact on the future environment. This requirement arises principally because of the technological challenges and high economic cost of removing these objects.By treating the space debris environment as a complex system and analysing the data using network and vertex measures, the debris problem can be understood from a new perspective. The aim of the current research is to demonstrate that network theory is an effective approach to analysing space debris environment data. Data from modelling studies are used to represent the space debris environment as networks. Vertices represent debris objects and edges represent the possible future conjunctions between the objects. The networks are analysed using the following measures: degree, strength, assortativity, affinity, clustering, and betweenness centrality. The results suggest that the space debris environment has a low average degree and is disassortative with hubs. This means that the environment is resilient to random removals as there are only a few vertices, the hubs, which may have a significant effect on the future environment. Furthermore, targeting the vertices with a high degree or betweenness centrality reduces the connectivity of a large space debris network by breaking it into several smaller networks. Therefore, a targeted ADR approach will be necessary if objects are removed from the space debris environment